Problem updating HDMI resolution on STM32MP157F-DK2 (LT6711A + IPS Mono LCD)

[nikbakhtfaezeh]

Hi,

I'm trying to change the HDMI output resolution of my STM32MP157F-DK2 board to support a BOE 13.3" Mono IPS LCD (connected via LT6711A HDMI to eDP bridge).

What I’ve done so far:

1. Extracted and edited the device tree source:

   • Decompiled stm32mp157f-dk2.dtb using dtc -I dtb -O dts.

   • Modified display-timings node to match my panel:

     dts

     CopyEdit

     timing0: timing0 { clock-frequency = <74250000>; // or appropriate pixel clock hactive = <1280>; vactive = <720>; hfront-porch = <110>; hback-porch = <220>; hsync-len = <40>; vfront-porch = <5>; vback-porch = <20>; vsync-len = <5>; hsync-active = <0>; vsync-active = <0>; de-active = <1>; pixelclk-active = <0>; };

2. Recompiled the DTS to DTB:

   • Used: dtc -I dts -O dtb -o stm32mp157f-dk2.dtb stm32mp157f.dts

3. Replaced DTB on SD card:

   • Mounted bootfs partition.

   • Copied new stm32mp157f-dk2.dtb to /bootfs/

4. Updated extlinux.conf:

   • Ensured that FDT /stm32mp157f-dk2.dtb is set correctly in:

     bash

     CopyEdit

     /boot/mmc0_extlinux/extlinux.conf

5. Verified after boot:

   • Device tree seems to load (checked /proc/device-tree/model and dtb name).

   • But /sys/class/drm/card0-HDMI-A-1/modes still only shows 720x480.

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Question:
Despite updating and loading the correct DTB, the HDMI output still defaults to 720x480. Is there a specific step or kernel option I’m missing to make the HDMI resolution switch correctly? Should I define a fixed mode via a hdmi-connector node or change something in the display controller node?

Thanks in advance!

[PatrickF]

Hi @nikbakhtfaezeh 

do this helps ?

https://wiki.st.com/stm32mpu/wiki/How_to_display_on_HDMI

Regards.